In vehicles or structures including slide-rooms, a flange assembly can be secured to the rear wall and/or roof of the slide-room that seals against the interior surface of the wall of the vehicle when the slide-room is in the extended position. However, such assemblies typically must be installed after the slide-room has been situated in the vehicle. The flange assemblies are typically secured using fasteners placed horizontally through the rear wall of the slide-room. However, due to limited space between the roof of the slide-room and the ceiling of the vehicle, it can be difficult or impossible to secure portions of the flange assembly disposed on the roof of the slide-room. The horizontally-oriented fasteners do not hold the flange assembly tightly against the interior wall of the vehicle, which can result in leakage past the flange into the interior of the vehicle. Additionally, the unsecured portions of the flange assembly disposed on the roof of the slide-room can be prone to movement or lifting when the flange assembly engages the interior wall of the vehicle, further contributing to leakage past the flange assembly. Thus, improvements to flange assemblies for slide-rooms are desirable.